Measurement Preparations - Bosch GTC 400 C Professional Originalbetriebsanleitung

20 | English
Note: In the first few minutes, the measuring tool may self-
calibrate several times, as the sensor temperature and ambi-
ent temperature have not yet been brought into line. Per-
forming sensor calibration again enables precise measure-
ment.
During this time, the temperature indicator may show ~. The
thermal image will freeze briefly during sensor calibration. If
the ambient temperature fluctuates significantly, this effect
is increased. If possible, you should therefore turn on the
measuring tool a few minutes before starting to measure, so
that the tool can stabilise thermally.
To switch off the measuring tool, press the on/off
button (9) again. The measuring tool saves all settings and
then switches itself off. Close the protective cap (1) to trans-
port the measuring tool safely.
In the main menu, you can choose whether and after how
long the measuring tool automatically switches off (see
"Main Menu", page 22).
If the battery pack or the measuring tool is not within the op-
erating temperature range specified in the technical data,
the measuring tool will switch off automatically after a brief
warning (see "Errors – Causes and Corrective Measures",
page 23). Allow the measuring tool to reach the correct
temperature and then switch it back on.

Measurement Preparations

Setting the emissivity for surface temperature
measurements
The emissivity of an object depends on the material and the
structure of its surface. This specifies how much infrared
thermal radiation the object emits compared with an ideal
radiant warmer (black body, emissivity ε = 1) and accord-
ingly has a value between 0 and 1.
To determine the surface temperature, the tool performs a
contactless measurement of the natural infrared thermal ra-
diation emitted by the object at which the tool is aimed. To
ensure correct measurement, the emissivity setting on the
measuring tool must be checked before every measure-
ment and adapted to the measuring object if necessary.
The preset emissivities in the measuring tool are reference
values.
You can select one of the preset emissivities or enter an ex-
act numerical value. Set the required emissivity via the
<Measurement> → <Emissivity> menu (see "Main Menu",
page 22).
Temperature measurements will only be correct if the
u
emissivity setting and the emissivity of the object
match.
The lower the emissivity, the greater the effect of the reflec-
ted temperature on the measuring result. Always adjust the
reflected temperature when changing the emissivity. Set the
reflected temperature via the <Measurement> →
<Reflected temp.> menu (see "Main Menu", page 22).
Temperature differences allegedly shown by the measuring
tool may be caused by different temperatures and/or differ-
ent emissivity levels. If the emissivity levels are very differ-
1 609 92A 7L1 | (20.05.2022)
ent, the depicted temperature differences may differ consid-
erably from the actual temperature differences.
If there are multiple objects made of different materials or
that have different structures in the measuring range, the
displayed temperature values are only accurate for the ob-
jects that match the emissivity setting. For all other objects
(with different emissivity levels), the displayed colour differ-
ences can be used as an indication of temperature relation-
ships.
Information about the Measuring Conditions
Highly reflective or shiny surfaces (e.g. shiny tiles or pol-
ished metals) may significantly distort or impair the results
shown. If necessary, mask the measuring surface with a
dark, matt adhesive tape that conducts heat well. Allow the
tape to briefly reach the correct temperature on the surface.
Make sure that a favourable measuring angle is used on re-
flective surfaces in order to ensure that the thermal radiation
reflected by other objects does not distort the result. For ex-
ample, the reflection of your own emitted body heat may in-
terfere with the measurement when measuring head-on from
a perpendicular position. On a level surface, the outline and
temperature of your body could therefore be displayed (re-
flected value), and these values do not correspond to the ac-
tual temperature of the measured surface (emitted value or
real value of the surface).
Measuring through transparent materials (e.g. glass or trans-
parent plastics) is fundamentally not possible.
Consequently, the more suitable and stable the measuring
conditions are, the more accurate and reliable the measure-
ment readings are. Not only do significant fluctuations in the
temperature of the environmental conditions have an im-
pact, the accuracy can also be impaired by significant fluctu-
ations in the temperatures of the object being measured.
Infrared temperature measurement is impaired by smoke,
steam/high humidity or dusty air.
Information for achieving improved measurement accuracy:
– Move as close as possible to the object to be measured to
minimise interfering factors between you and the surface
to be measured.
– Ventilate indoor areas prior to measurement, especially
when the air is contaminated or extremely steamy. Once
ventilated, allow the room to reacclimatise a while until it
returns to the usual temperature.
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